In a process of manufacturing a semiconductor device, operations are carried out a number of times. The operations include film formation making use of sputtering and/or chemical vapor deposition, flattening making use of chemical/mechanical polishing and patterning making use of lithography and/or etching. In order to sustain a high yield of the semiconductor device, the wafer is pulled out from the manufacturing process and inspected for a defect.
The defect existing on the surface of the wafer is a foreign substance, a bulge, a scratch or a pattern defect (such as a short, an opening or a hole aperture defect).
A first objective of the inspection for a defect is management of conditions of the manufacturing apparatus whereas a second objective thereof is identification of a process generating the defect and a cause of the defect. With the semiconductor device becoming finer and finer, the defect inspecting apparatus is required to have a high detection sensitivity.
On the wafer, several hundreds of devices (each referred to as a chip) having the same pattern are created. In addition, in typically a memory of the device, a large number of cells having repetitive patterns are created. The defect inspecting apparatus adopts a method of comparing images of adjacent chips or images of adjacent cells with each other.
An optical defect inspecting apparatus for taking an image of a wafer by radiating light to the wafer has a high throughput in comparison with a defect inspecting apparatus of another type. Thus, a large number of optical defect inspecting apparatus are used for inline inspection. An example of the defect inspecting apparatus of another type is a defect inspecting apparatus radiating an electron beam or the like to a wafer.
The conventional optical defect inspecting apparatus is described in patent reference 1 which is JP-A-2005-521064. In the conventional optical defect inspecting apparatus described in patent reference 1, a plurality of movement lenses generate a plurality of spot beams from a beam generated by a laser-beam source and the spot beams are then radiated to a wafer. While the spot beams are being used for scanning lines, detectors for the spot beams are moved in parallel to give a high throughput in comparison with a defect inspecting apparatus making use of a single spot beam.
Other technologies are described in patent references 2 to 4.